The present disclosure relates generally to loudspeaker systems. More particularly, the present disclosure relates to arrays of commercial loudspeaker array elements.
Large arrays of full frequency range loudspeakers have been the standard for producing high sound pressure levels for concert production and performance installation for several decades. In the early days of professional audio, loudspeaker array designers attempted to direct audio three dimensionally in clusters of loudspeakers known as spherical arrays. Since the turn of the millennium many array designs have involved a vertical row of loudspeaker enclosures arranged symmetrically on either side of a centrally oriented vertical slot, energized by high frequency transducers. This has become known as the line array.
Array elements are generally connected one to another by a rigging system attached directly to the enclosure to form the array. Rigging systems generally include adjustable metal parts allowing the desired angular relationship between the elements of the array to be achieved. In order to achieve a curved array, rigging systems are typically provided with two sets of components, one set mounted near the front of and the other mounted near the back of the enclosure. By this method a stable curved array may be formed.
The desired array geometry is most often determined by dedicated simulation software that predicts the likely acoustic behaviour of the array in the listening environment. Based on the simulation software the geometry is optimized prior to array assembly so that when erected the individual array elements point at the exact prescribed locations in the listening area creating even sound pressure distribution. Because of the limited length of the array and the geometry of typical listening environments, the shape of the array is typically curved and most often the curvature increases toward the lower portion of the array. A precise and predictable angular setting between the elements is therefore essential.
The overwhelming material of choice for the primary structure of the loudspeaker enclosure has been wood in one form or another, although in recent years many new materials have been introduced. The benefits of wooden construction for low and mid frequency reproduction are known. Wood construction is acoustically beneficial when sound pressure from the rear of a speaker cone interacts with the wooden enclosure directly.
In sealed back chamber transducers, which may be used for mid and high frequency reproduction, the sound pressure is contained within the transducer and a molded horn or chamber that is isolated from the enclosure surrounding it. In this form there is no benefit to enclose these transducers in a wooden enclosure.
While wood exhibits acoustic properties that are beneficial, there are many limitations associated with its manufacturing characteristics and structural properties. The manufacturing process of wooden enclosures often results in dimensional deviations from the product specification. Where rigging systems are attached directly to a wooden array element mechanical stresses from assembling and erecting (flying) an array or from transportation may cause added distortions. These dimensional variations may result in inaccurate angles between array elements causing a distortion of the desired curvature of the array.
Furthermore, additional temporary dimensional distortions may arise from mechanical flexural stresses induced in the array elements when the weight of the entire array is borne by the rigging systems. As elements are added to the array, the flexing of the uppermost wooden components increases dramatically, resulting in load dependent angular changes within the array.
Given the structural disadvantages of wooden enclosures, composite materials are sometimes used for enclosures. Array elements built with these enclosures can be more accurately constructed allowing for faster assembly during manufacturing. Additionally, they are less likely to deviate due to mechanical stress resulting in an element that is less likely to suffer from rigging misalignment during array assembly. However, using a composite enclosure does not take advantage of the acoustical benefits of wooden enclosures.
In the typical manufacturing environment, manual labor is employed in the assembly and finishing of the wooden loudspeaker enclosure. The wooden enclosure component of a large array element can be unwieldy and difficult to handle in the production environment as it might weigh more than 100 lbs. Whether the enclosure is wood or composite material current array elements may be quite large and heavy when fully assembled. Dimensions of up to 58″ wide×27″ depth×18.5″ height and weight of up to 270 lbs are not uncommon.
Another characteristic of the wooden loudspeaker enclosure is that wood is a thermal insulator. Generally, low frequency enclosures are acoustically vented to enhance efficiency. A byproduct of this venting is that heat dissipation from the low frequency transducer is aided by air movement through the enclosure vent. When heat generating electronic equipment or an unvented transducer such as a high or mid frequency horn transducer is added to a wooden loudspeaker enclosure, metal heat sinking or some other method of heat removal becomes an important consideration since the wood will limit the dissipation of excess heat from the system.
Arrays of low frequency array elements have also become popular in recent years. The problems associated with low frequency array elements are similar to those encountered with full range array elements. One important difference is that most low frequency array elements are rectangular in cross section and therefore low frequency arrays are generally not curved (although curvature may be required in some instances). In many cases, low frequency elements are significantly larger than the full range elements with which they operate.
In the manufacturing environment, in all phases beyond primary assembly, the size and weight of low frequency array elements poses challenges to workers. Specifically, the wood enclosure assembly, paint preparation, painting and installation of all components each poses a particular difficulty when the size and weight of the array element exceeds the size and weight that can be managed by a single worker.